Method and apparatus for handling emergency calls in a packet switched radio access network

Abstract

A method and apparatus for providing location information for subscribers connected to a packet-switched mobile access network in connection with emergency calls made over a multimedia service network. An emergency request is received at the multimedia service network from a subscriber containing the calling number of the subscriber. In response thereto, a media gateway control function in the multimedia service network sends a location query including the calling number to a mobile positioning center in the mobile access network, which then can retrieve location information for the subscriber. After receiving location information from the mobile positioning center, the media gateway control function selects an emergency center and sends a location indication for the subscriber thereto in a circuit-switched control message for initiating an emergency call, according to prevailing standards.

1. A method in a multimedia service network of providing location information to an emergency center in a circuit-switched network for a mobile radio terminal connected to a packet-switched mobile access network, comprising the following steps:
 receiving a packet-switched emergency request from the mobile radio terminal containing a calling number, 
 sending a location query for said calling number to a mobile radio terminal positioning center in a mobile radio access network when more detailed location information is needed, 
 receiving a location indication for the mobile radio terminal in response to the location query, 
 translating the packet-switched emergency request into a circuit-switched control message for said emergency request, and 
 sending the translated circuit-switched control message including the location indication for the mobile radio terminal to the emergency center according to prevailing standards for initiating a circuit-switched emergency call, 
 wherein the method is executed in a media gateway control function node, coupled to the mobile radio terminal positioning center, a packet-switched core network node coupled to the mobile radio access network, and the emergency center, that translates packet-switched signalling messages into circuit-switched signalling messages to emulate the behavior of a circuit-switched network towards the emergency center, 
 wherein the multimedia service network is an IP Multimedia Subsystem (IMS) network using Session Initiation Protocol (SIP) signalling, and 
 wherein the emergency request is an SIP INVITE message. 
 
     
     
       2. A method according to  claim 1 , wherein the media gateway control function emulates the behavior of a mobile switching center (MSC) in a circuit-switched mobile access network, using an Lg interface or E3 interface as specified in the J-STD-036-A standard. 
     
     
       3. A method according to  claim 1 , wherein said emergency center is selected for the request based on the received location information. 
     
     
       4. A method according to  claim 1 , wherein said location indication indicates the current location of the mobile radio terminal as geographic coordinates or a street address. 
     
     
       5. A method according to  claim 1 , wherein said location indication indicates the current location of the mobile radio terminal using a reference code or pointer such that the emergency center can use the location indication to retrieve location information from the mobile positioning center, if needed. 
     
     
       6. A method according to  claim 5 , wherein the received location information is sent on an Lg interface or E3 interface as specified in the J-STD-036-A standard to the mobile positioning center, and said reference code or pointer is then received as a response from the mobile positioning center on said Lg interface or E3 interface. 
     
     
       7. A method according to  claim 1  wherein the circuit-switched control message is an IAM message according to the ISUP standard. 
     
     
       8. An arrangement in a multimedia service network for providing location information to an emergency center in a circuit-switched network for a mobile radio terminal connected to a packet-switched mobile access network, comprising:
 means for receiving a packet-switched emergency request from the mobile radio terminal containing a calling number, 
 means for sending a location query for said calling number to a mobile radio terminal positioning center in a mobile radio access network when more detailed location information is needed, 
 means for receiving a location indication for the mobile radio terminal in response to the location query, 
 means for translating the packet-switched emergency request into a circuit-switched control message for said emergency request, and 
 means for sending the translated circuit-switched control message including the location indication for the mobile radio terminal to the emergency center according to prevailing standards for initiating a circuit-switched emergency call, 
 wherein the arrangement is implemented in a media gateway control function node coupled to the mobile radio terminal positioning center, to a packet-switched core network node, and to the emergency center, the media gateway control function node being configured to translate packet-switched signalling messages into circuit-switched signalling messages to emulate the behavior of a circuit-switched network towards the emergency center, 
 wherein the multimedia service network is an IMS network using SIP signalling, and 
 wherein said emergency request is an SIP INVITE message. 
 
     
     
       9. An arrangement according to  claim 8 , wherein the media gateway control function is configured to emulate the behavior of an MSC in a circuit-switched mobile access network using an Lg interface or E3 interface as specified in the J-STD-036-A standard. 
     
     
       10. An arrangement according to  claim 8 , further comprising logic means for selecting said emergency center for the request based on the received location information. 
     
     
       11. An arrangement according to  claim 8 , wherein said location indication indicates the current location of the mobile radio terminal as geographic coordinates or a street address. 
     
     
       12. An arrangement according to  claim 8 , wherein said location indication indicates the current location of the mobile radio terminal using a reference code or pointer such that the emergency center can use the location indication to retrieve location information from the mobile positioning center, if needed. 
     
     
       13. An arrangement according to  claim 12 , further comprising means for sending the received location information on an Lg interface or E3 interface as specified in the J-STD-036-A standard to the mobile positioning center, and means for receiving said reference code or pointer as a response from the mobile positioning center on said Lg interface or E3 interface. 
     
     
       14. An arrangement according to  claim 8 , wherein the circuit-switched control message is an IAM message according to the ISUP standard.